1. Field of the Invention
This invention relates to an information recording and reproducing apparatus of the rotary head type such as, for example, a digital audio tape recorder which records a plurality of channels of record data in a two-track completion interleave condition onto a recording medium and reproduces record data recorded in a two-track completion interleave condition on a recording medium.
2. Description of the Prior Art
Information recording and reproducing apparatus of the type mentioned are already known. A typical one of such information recording and reproducing apparatus is a digital audio tape recorder. FIG. 6 shows a general construction of conventional digital audio tape recorders.
Referring to FIG. 6, the conventional digital auto tape recorder shown has an input terminal 1 for receiving an input analog signal. The analog signal received is supplied to a low-pass filter 2 having a cutoff frequency equal to one half the sampling frequency. Thus, the low-pass filter 2 passes therethrough an analog signal component of any frequency of the received analog signal lower than the cutoff frequency.
An analog to digital (A/D) converter 3 converts the analog signal supplied thereto from the low-pass filter 2 into a digital signal, and an error correction code addition circuit 4 interleaves the digital signal (record data) supplied thereto from the analog to digital converter 3 and writes the interleaved digital signal into a RAM provided therein. The error correction code addition circuit 4 then generates a correction code reads out the record data from the RAM, adds the error correction code to the record data, and interleaves and writes the record data back into the RAM. Finally, the error correction code addition circuit 4 outputs the record data successively.
Also some other record data such as a sub code are supplied from a circuit not shown to the error correction code addition circuit 4, written into the RAM, and outputted from the error correction code addition circuit 4.
The record data of 8 bits outputted from the error correction code addition circuit 4 are modulated into record data of 10 bits by an 8-10 modulation circuit 5. The record data of 10 bits from the 8-10 modulation circuit 5 are amplified by a recording amplifier 6 and supplied to a pair of magnetic heads 8a and 8b provided at opposite locations of a rotary head 8 by way of a change-over switch 7. The change-over switch 7 has a contact 7c which is changed over to a contact 7a or another contact 7b when an operation key of an operation section 15 is operated to establish a predetermined operation mode. The contact 7a of the change-over switch 7 is connected to the recording amplifier 6. Meanwhile, the magnetic heads 8a and 8b are connected to the contact 7c of the change-over switch 7.
The low-pass filter 2, the analog to digital converter 3, the error correction code addition circuit 4, the 8-10 modulation circuit 5 and the recording amplifier 6 constitute a recording system of the digital audio tape recorder.
A reproduction amplifier 9 is connected to the contact 7b of the change-over switch 7, and based on reproduction data from the reproduction amplifier 9, a synchronizing signal for controlling a control system, an ATF signal and so forth are generated by a circuit not shown.
A 10-8 demodulation circuit 10 demodulates the reproduction data of 10 bits supplied thereto from the reproduction amplifier 9 into reproduction data of 8 bits. An error detection and correction circuit 11 writes the reproduction data of 8 bits supplied thereto from the 10-8 demodulation circuit 10 once into a RAM therein. The error detection and correction circuit 11 then reads out the reproduction data from the RAM and writes, if the reproduction data have no error, the reproduction data as they are back into the RAM, but corrects, if the reproduction data have an error, the reproduction data and writes them into the RAM. The error detection and correction circuit 11 thereafter outputs the reproduction data successively.
The reproduction data in the form of a digital signal supplied thereto from the error detection and correction circuit 11 are converted into an analog signal by a digital to analog (D/A) converter 12. A low-pass filter 13 receives the analog signal from the digital to analog converter 12 and passes therethrough an analog signal component of any frequency of the received analog signal lower than its cutoff frequency. The output of the the low-pass filter 13 is outputted to an output terminal 14.
Though not shown, the operation section 15 includes a plurality of operation keys for manual operation by the user of the digital audio tape recorder. The operation section 15 is connected by way of a suitable control circuit not shown to the changeover circuit 7 and driving and controlling apparatus not shown of the digital audio tape recorder including a driving apparatus for the rotary head 8 such that the contact 7c of the change-over switch 7 is selectively changed over to the contact 7a or the other contact 7b and the driving and controlling apparatus are selectively put into one of several operation modes in response to operation of one of the operation keys.
A magnetic tape T as a recording medium is transported in the direction indicated by an arrow mark D.sub.T, and record data are recorded onto or reproduced from the magnetic tape T by the magnetic heads 8a and 8b of the rotary head 8. The rotary head 8 is rotated in the direction indicated by an arrow mark D.sub.H by the driving apparatus therefor.
In operation, when a recording key, which is one of the operation keys of the operation section 15, is manually operated, the contact 7c of the change-over switch 7 is changed over to the contact 7a to establish a recording mode of the digital audio tape recorder. Consequently, an input analog signal supplied to the input terminal 1 is first processed in such a manner as described above by the recording system and then supplied as record data to the magnetic heads 8a and 8b of the rotary head 8 by way of the change-over switch 7 so that it is recorded onto the magnetic tape T.
On the other hand, when a reproduction key, which is another one of the operation keys of the operation section 15, is manually operated, the contact 7c of the change-over switch 7 is changed over to the contact 7c to establish a reproduction mode of the digital audio tape recorder. Consequently, reproduction data are reproduced from the magnetic tape T by the magnetic heads 8a and 8b and supplied to the reproduction system of the digital audio tape recorder by way of the change-over switch 7. The reproduction data are thus processed in such a manner as described above by the reproduction system and thereafter supplied as an analog signal to the output terminal 14.
FIGS. 7a and 7b illustrate a process if forming recording tracks on a magnetic tape by means of magnetic heads. Referring to FIGS. 7a and 7b, reference character Tr.sub.a denotes a record track formed on the magnetic tape T by the magnetic head 8a, Tr.sub.b another record track formed on the magnetic tape T by the other. magnetic head 8b, and Tr.sub.a1 a further record track, which is formed by final shaping of the record track Tr.sub.a by the magnetic head 8b.
Reference character D.sub.HR denotes the direction of transportation of the magnetic heads 8a and 8b, reference characters L.sub.1.5a and L.sub.1.5b denote center lines of the record tracks Tr.sub.a and Tr.sub.b, and reference character L.sub.1.0 denotes a center line of the record track Tr.sub.a1.
Reference character W.sub.1.5 denotes a magnetic head width of the magnetic heads 8a and 8b, that is, a width of the record tracks Tr.sub.a and Tr.sub.b, W.sub.1.0 a width of the record track Tr.sub.a1, W.sub.0.5 a width over which the record track Tr.sub.a and the record track Tr.sub.b overlap with each other, and the width W.sub.1.0 is equal to two thirds the width W.sub.1.5 while the width W.sub.0.5 is equal to one third the width W.sub.1.5.
FIG. 8 is shows an arrangement of record tracks formed on a magnetic tape. Referring to FIG. 8, reference characters Tr.sub.1 to Tr.sub.24 denote record tracks formed finally on the magnetic tape T by the magnetic heads 8a and 8b. Various control data are recorded together with record data of the L and R channels on the record tracks Tr.sub.1 to Tr.sub.24.
It is to be noted that one frame is constituted from record data interleaved on each pair of record tracks Tr.sub.(2n-1) and Tr.sub.2n and, for example, the record track Tr.sub.(2n-1) is recorded or reproduced by the magnetic head 8a while the record track Tr.sub.2n is recorded or reproduced by the magnetic head 8b.
Further, for example, odd-numbered data of the L channel and even-numbered data of the R channel are recorded onto the record track Tr.sub.(2n-1) while even-numbered data of the L channel and odd-numbered data of the R channel are recorded onto the record track Tr.sub.2n.
Subsequently, the positions of the magnetic heads upon formation of record tracks and upon reproduction of such record data will be described with reference to FIGS. 7a, 7b and 8.
Referring first to FIG. 7a, the record track Tr.sub.a of the width W.sub.1.5 is formed by the magnetic head 8a with the equal widths distributed on the left and right sides of the center line L.sub.1.5a.
Meanwhile, as shown in FIG. 7b, the record track Tr.sub.b of the width W.sub.1.5 is formed by the magnetic head 8b with the equal widths distributed on the left and right sides of the center line L.sub.1.5b such that the record track Tr.sub.b may overlap with a portion of the record track Tr.sub.a having a width equal to one third the width W.sub.1.5.
Since the record track Tr.sub.a is shaped by the magnetic head 8b in this manner, it finally makes a record track Tr.sub.a1 having a center line L.sub.1.0a displaced from the center line L.sub.1.5a of the record track Tr.sub.a with the equal widths distributed on the left and right sides of the center line L.sub.1.0a.
Also the record track Tr.sub.b is shaped similarly by the magnetic head 8a so that, similarly to the record track T.sub.ra1, finally the center line L.sub.1.5b thereof is moved to the position of the center line L.sub.1.0b to make another record track (not shown) which has the width W.sub.1.0 with the equal widths distributed on the left and right sides of the center line L.sub.1.0b.
Consequently, the record tracks Tr.sub.1 to Tr.sub.24 of the width W.sub.1.0 which is equal to two thirds the width W.sub.1.5 of the magnetic heads 8a and 8b are formed on the magnetic tape T as shown in FIG. 8.
When the record data are to be reproduced from the magnetic tape T, the centers of the magnetic heads 8a and 8b (centers of the magnetic head widths) trace the center lines L.sub.1.01 and L.sub.1.0b of tracks so that the record data can be reproduced by the magnetic heads 8a and 8b.
Since the conventional information recording and reproducing apparatus of the rotary head type is constructed in such a manner as described above, record data can be recorded onto and reproduced from a magnetic tape.
In a multi-track digital audio tape recorder of the type described above, it sometimes occurs for convenience of use that the user later wants to re-record only for data of a predetermined channel or only for data of a predetermined portion of a predetermined channel.
When re-recording for data is to be performed in this manner, since the data are recorded in an interleaved condition, not only data to be re-recorded but also other record data, that is, all record data corresponding to the record data on the magnetic tape, must be prepared, and the entire data must be re-recorded.